Hutchinson-Gilford Progeria syndrome (HGPS, OMIM 176670) is a rare disorder that is characterized by accelerated aging and early death, frequently from coronary artery disease. Mutations in the LMNA gene are responsible for this syndrome; as such HGPS belongs to the super-family of laminopathies. The most common HGPS mutation corresponds to G608G (GGC>GGT), within exon11 of LMNA, which elicits a deletion of 50 amino acids at the carboxyl-terminal tail domain of prelamin A; the resulting product is denoted progerin. The lamins are structural nuclear proteins that bind to many important nuclear regulators, and therefore, may play a role in regulating the accessibility of those regulators to fulfill their function. The progerin mutation exhibits a tissue specific pattern of alterations, involving primary tissues with renewal potency: muscle, skin, and bone. In our preliminary studies, we succeeded in generating a polyclonal antibody that specifically recognizes progerin. This is the first such tool in the field; it detects the truncated lamin A product progerin in HGPS G608G fibroblasts. Indirect immunofluorescence studies also revealed that the progerin protein accumulates gradually within the nuclear compartment reaching an expression level that induces a dramatic disruption of the nuclear lamin network. Based on these observations, we hypothesize that progerin products accumulate in the nucleus in an age-dependent manner and acts as a dominant negative mutant by altering the nuclear lamin networks; this ultimately affects cellular functions such as cell-cycle progression. To test this hypothesis we propose three specific aims: (1) Combine biochemical and morphological analysis to determine how progerin acts in a spatio-temporal manner on the organization and function of the nucleus; (2) Identify and characterize proteins that interact with lamin A but not with progerin and link them to functional pathway(s); (3) Determine whether cellular, nuclear and functional alterations identified in HGPS G608G fibroblasts are also altered in a similar manner in other lamin A-associated premature aging disorders, such as atypical and adult progeroid syndromes.